1. Field of the Invention
The present invention relates to systems and methods that are used to control ancillary telecommunications equipment to facilitate proper call routing and processing in a telecommunications network.
2. Description of the Related Art
In modern call processing networks such as those incorporating digital call transport systems, ancillary telecommunications devices such as echo suppressors and cancellers are used to process and service calls. Typically, the use of such ancillary telecommunications devices is triggered by the nature and type of call to be serviced. For example, voice calls, in contrast to data calls, often require echo control within a call path to negate the effects of echo and the like. To invoke an ancillary device such as an echo canceller to service a call, the same must be activated/deactivated in response to a control signal sent from an instructing switching system such as during an initial request for service or other call setup sequence. Typically, switching systems such as inter-exchange switching systems, control ancillary telecommunications devices through use of well known signaling techniques which are in general use in modern telecommunications networks. Typically, control of ancillary telecommunications devices is achieved (and limited) by such signaling techniques.
Such signaling techniques are used to pass call control signals from one telecommunications network element to another to effect proper call routing and processing. Ancillary telecommunications devices take advantage of such signaling techniques to automatically activate/deactivate to service calls. Such signaling techniques are known as Channel Associated Signaling (CAS) and Common Channel Signaling (CCS).
In a CAS environment, call control is achieved through use of signaling bits within a call""s data-payload to pass control signals between switching elements and to alert the presence of calls in a telecommunications network. For example, in channelized DS-1 applications, per-channel circuit signaling may be achieved by allowing every 6th data frame and, in particular, the least significant bit thereof (i.e., the eight bit of each time slot) to be used or xe2x80x9crobbedxe2x80x9d for signaling purposes. Accordingly, CAS signaling has often been referred to as xe2x80x9crobbed bitxe2x80x9d signaling.
Such signaling bits also may be used to indicate the presence of an incoming call to an ancillary telecommunications device that exists in a particular call path. Ancillary devices such as echo cancellers, etc., monitor signaling bit status and activate/deactivate accordingly (e.g., turn themselves on or turn themselves off). Unfortunately, typical call setup processes and systems set the signaling bits at the beginning of a call (e.g., to affect ancillary devices, etc.) and leave those bits as set throughout the duration of the call. Currently, there is no way to control such signaling bits to effect intra-call control of an ancillary telecommunications device.
In a xe2x80x9csuperframe formatxe2x80x9d (SF) CAS environment as defined in ANSI Standards Document T1.107-1995, bits may be robbed for signaling from every 6th and 12th frames that make up a superframe (i.e., 12 frames) of channelized call data. In particular, the bit from the 6th frame of a superframe is commonly referred to as the xe2x80x9cAxe2x80x9d bit, while the robbed bit from the 12th frame of a superframe is commonly referred to as the xe2x80x9cBxe2x80x9d bit. In an extended superframe (ESF) arrangement where 24 frames consisting of 24 channels per frame are provided and processed, signaling bits may be robbed from every 6th, 12th, 18th and 24th frames which are respectively referred to as xe2x80x9cA,xe2x80x9d xe2x80x9cB.xe2x80x9d xe2x80x9cC,xe2x80x9d and xe2x80x9cDxe2x80x9d signaling bits. Depending the nature of the signaling to be performed (e.g., switch control for routing or pre-/post-call control of ancillary telecommunications devices, etc.), each bit of the signaling channels derived by the aforementioned signaling bits may take on one of two states (i.e., ON or OFF). Accordingly, depending on the number of signaling bits provided in a CAS environment, for example, 2n (where n is the number of signaling bits) signaling combinations (i.e., bit sequences) may be used for control purposes. Unfortunately, however, signaling bits take up valuable payload area in a CAS environment that could otherwise be used for transport of call content.
To address the use of payload bits for signaling as in the case of a CAS signaling environment, CCS signaling was developed and now is widely deployed. In a CCS environment (e.g., similar or like an SS7 network, etc.), signaling and call control for call setup are passed between network elements on a disassociated channel outside of a call""s payload channels. Accordingly, a payload channel retains all payload bits without signaling schemes requiring robbed bits and the like.
Despite their flexibility, CAS and CCS signaling environments are not without their problems especially with regard to controlling ancillary telecommunication equipment. For example, in both CAS and CCS signaling environments, the way signaling bits may be used is limited. In particular, in a CAS environment, a signaling state exists for on-hook and off-hook conditions for a number of different signaling formats (e.g., Ear and Mouth signaling (EandM), etc.), thus requiring ancillary devices to be configured to monitor for a host of activate/deactivate conditions. Additionally, signaling states may only be changed at the onset or termination of a call connection. There can be no intra-call change of signaling states that may be used to control ancillary telecommunications devices.
And, since there are no xe2x80x9csignaling bitsxe2x80x9d within a payload envelope in CCS signaling environment (since CCS uses a separate, disassociated network for signaling that frees bits that are otherwise used in CAS environment for signaling), ancillary equipment must rely on the detection of idle codes within a payload envelope to detect the onset of a next call event (e.g., on-hook, etc.). As such, the use of internal processes such as continuity tests (COT tests) on inter-machine trunks (IMTs) can cause ancillary devices like echo cancellers to false-trigger and begin operating prior to the onset of a call. And, like CAS signaling environments, call connection changes in a CCS signaling environment cannot be made during or once a call connection is established.
In addition to the CAS and CCS signaling paradigms discussed above, other signaling methods to extend call-by-call control of ancillary telecommunications equipment have been proposed. Although such methods have many merits, they also have limitations that ultimately preclude their use to effect control of ancillary telecommunications devices. Such other signaling methods include facility data link (FDL) signaling and external lead signaling. The use of FDL signaling requires a network that supports extended superframe line formatting. External lead based signaling utilizes an external control link from a switching platform to ancillary devices within a telecommunications network. Although external lead based signaling and control will allow needed ancillary device control, the same introduces many problems associated with cable and line management and database administration that would prove to be substantial in larger telecommunications networks.
Thus, there exists a need to provide systems and methods that will enhance signaling operations within CAS and CCS environments to effectively and efficiently control ancillary telecommunications equipment before, during, and after call establishment. Such systems and methods must operate within current signaling systems without requiring significant platform and infrastructure modifications. To be viable, such systems and methods must allow existing signaling techniques and systems to be redefined to support new and different signaling needs.
The present invention solves the problems associated with prior signaling systems to allow ancillary telecommunications devices to be controlled before, during, and after call set-up and other call processing operations. Such control is achieved in accordance with the present invention by affecting signaling bits in a channel associated signaling (CAS) environment, and payload data within a common channel signaling (CCS) environment. For example, in a CCS signaling environment ancillary telecommunications devices such as echo cancellers are normally set to be in an inactive or bypass (deactivated) state prior to call set-up. Upon receipt of a call that requires an echo canceller to be active (i.e., to counteract the effects of echo in a voice call, etc.), a switch sets outbound xe2x80x9csignaling bitsxe2x80x9d high for a certain number (e.g., 12) of standard signaling frames (thus activating the echo canceller) and then reverts the data channel(s) containing the call to a clear channel mode (i.e., to a mode that allows complete usage of call data channels). In a CCS context, there are no signaling bits within a payload envelope; the present invention redefines payload bits (for relatively short periods of time) to facilitate intra-call control of ancillary telecommunications devices. An echo canceller in such a scenario converts to an active mode until signalled by signaling switch with another set of signaling frames having signaling bits set high. Intra-call control of an echo canceller, for example, is achieved by the present invention by affecting the signaling bits (e.g., via signal modulation, cancellation, etc.) in a prescribed way (based on operational parameters of a particular echo canceller) for a particular number of frames and/or for a particular amount of time. Accordingly, in a CCS environment data channels related to a call are affected only for a definite, relatively short period of time (e.g., for a certain number of frames) related to signaling to control one or more echo cancellers. Thus, ancillary device control during as well as before and after a call according to the present invention also will allow full channel bandwidth utilization for call payload processing.
In a CAS environment, in contrast to a CCS environment, signaling bits are in use during the course of the call connection (i.e., are part of a call""s payload). However in an EandM (ear and mouth) signaling environment, for example, an xe2x80x9cAxe2x80x9d bit may be used to support the call connection thereby allowing a xe2x80x9cBxe2x80x9d bit to be modulated (during a call, for example) in accordance with the present invention to activate/deactivate an echo canceller as described above with regard to a CCS environment. The main drawback here is the limited bandwidth that the xe2x80x9cBxe2x80x9d bit represents (e.g. one bit may be set to either an ON state or an OFF state thus possibly requiring additional successive frames for signaling state changes, etc.). Accordingly, the present invention now allows CAS signaling environments to redefine the use of certain signaling bits within channelized data to effect control of ancillary telecommunications devices. Because control of such devices may be achieved by modulating or otherwise affecting payload data for only relatively short periods of time (e.g., for a certain number of data frames, etc.), little to no effect on communications, especially voice communications, will be realized. And, any such adverse effects that may be realized will be counterbalanced and, possibly, negated by the gains in control that result from intra-call control of ancillary telecommunications devices.
The present invention achieves the aforementioned functionality by providing systems and methods for controlling a telecommunications device such as an echo canceller within a telecommunications system. The systems and methods include and involve a switching system that is configured to receive a call from a calling station and to route said call within said telecommunications system and an ancillary telecommunications device that is configured to control a call processing parameter to affect said call. The switching system and the ancillary telecommunications device are coupled to each other via a channelized call data network. The channelized call data network is configured to communicate data corresponding to the call over at least one data channel. The ancillary telecommunications device controls the call processing parameter to affect the call based on a directive issued by the switching system to the ancillary telecommunications device during the call. The directive is contained within at least one channel of the channelized call data network. The channelized call data network may be completely used for call processing and call payload transport even after the ancillary telecommunications device operates as directed (e.g., activates, deactivates, etc.) during the call.
The above-summarized aspects of the present invention are described in detail below with regard to the attached drawing figures which are next discussed.